public bool AddURLToFrontQueue(PrettyURL url)
{
// tjek om allerede besøgt
if (AllURLS.Contains(url.GetPrettyURL.GetHashCode()))
{
return false;
}
int rand = new Random().Next(0, FrontQueues.Count);
FrontQueues[rand].Enqueue(url);
AllURLS.Add(url.GetPrettyURL.GetHashCode());
return true;
}
/// <summary>
/// Parse robots.txt from a specific prettyURL.
/// Assumes robots.txt is properly formatted.
/// </summary>
/// <param name="prettyURL"></param>
/// <param name="robotsContent"></param>
/// <returns>A regex to determine if a prettyURL is disallowed.</returns>
private Regex CalcRobotRegexForDomain(PrettyURL url, IEnumerable<string> robotsContent)
{
if (CachedRegexes.ContainsKey(url.GetDomain) && DateTime.Now - CachedRegexes[url.GetDomain].Item1 < MaxAge)
{
return CachedRegexes[url.GetDomain].Item2;
}
regexCalcWatch.Restart();
// No restrictions
//
if (robotsContent == null || robotsContent.Count() == 0)
{
return new Regex(@"@.");
}
// Find what is disallowed.
var disallow = robotsContent.SkipWhile(s => !Regex.IsMatch(s, @"User-Agent: \*", RegexOptions.IgnoreCase)) // Start from user agent *.
.TakeWhile(s => !string.IsNullOrWhiteSpace(s)) // Read until blank line (where allow/disallow hopefully ends).
.Skip(1) // Skip the user agent string.
.Where(s => s.StartsWith("Disallow")) // We only need disallowed stuff.
.Select(s => s.Split(':').Last().Trim()); // Select the disallowed stuff.
if (disallow.Count() == 0)
{
return new Regex(@"$.");
}
// Build the regex string
StringBuilder regPattern = new StringBuilder(url + "(" + disallow.First());
foreach (var s in disallow.Skip(1))
{
regPattern.Append('|');
//regPattern.Append(prettyURL);
regPattern.Append(s);
}
regPattern.Append(')');
regPattern.Replace("*", ".*").Replace(".", "\\.").Replace("+", "\\+");
CachedRegexes[url.GetDomain] = new Tuple<DateTime, Regex>(DateTime.Now, new Regex(regPattern.ToString()));
regexCalcWatch.Stop();
regexCalcTimes[url.GetDomain] = (int)regexCalcWatch.Elapsed.TotalMilliseconds;
return CachedRegexes[url.GetDomain].Item2;
}
public bool IsVisitAllowed(PrettyURL url)
{
if (CachedRegexes.ContainsKey(url.GetDomain))
{
// Too old?
if (DateTime.Now - CachedRegexes[url.GetDomain].Item1 > MaxAge)
{
var robotContent = DownloadRobotContent(url).Split('\n');
var regex = CalcRobotRegexForDomain(url, robotContent);
CachedRegexes[url.GetDomain] = new Tuple<DateTime, Regex>(DateTime.Now, regex);
}
}
else
{
var robotContent = DownloadRobotContent(url).Split(new string[] { "\r\n", "\n" }, StringSplitOptions.None);
var regex = CalcRobotRegexForDomain(url, robotContent);
CachedRegexes[url.GetDomain] = new Tuple<DateTime, Regex>(DateTime.Now, regex);
}
return !CachedRegexes[url.GetDomain].Item2.IsMatch(url.GetPrettyURL);
}
public void RemoveRobot(PrettyURL url)
{
CachedRegexes.Remove(url.GetDomain);
}
private string DownloadRobotContent(PrettyURL url)
{
string content = "";
robotDownloadWatch.Restart();
try
{
string robot = "http://" + url.GetDomain + "/" + "robots.txt";
//System.Diagnostics.Debug.WriteLine("Downloading " + robot);
content = new System.Net.WebClient().DownloadString(robot);
}
catch (Exception ex)
{
//System.Diagnostics.Debug.WriteLine("Robot: Could not download " + url);
}
robotDownloadWatch.Stop();
robotDownloadTimes[url.GetDomain] = (int)robotDownloadWatch.Elapsed.TotalMilliseconds;
return content;
}
public IEnumerable<PrettyURL> ExtractLinksFromHTML(PrettyURL url, string html)
{
if (html == null)
{
return Enumerable.Empty<PrettyURL>();
}
var hrefs = html.Split(new string[] { "<a href=\"" }, StringSplitOptions.RemoveEmptyEntries)
.Skip(1)
.Where(s => !s.StartsWith("feed") && !s.StartsWith("javascript"));
var urls = new List<PrettyURL>();
foreach (var href in hrefs)
{
var link = href.Split('\"').First();
string fullPath = (link.StartsWith("/") ? url.GetPrettyURL : "") + link;
if (PrettyURL.IsValidURL(fullPath))
{
var pretty = new PrettyURL(fullPath);
if (pretty.GetDomain.EndsWith(".dk"))
{
urls.Add(new PrettyURL(fullPath));
}
}
}
return urls;
}
public string DownloadHTML(PrettyURL url)
{
WebClient web = new WebClient();
if (Robot_IAm.IsVisitAllowed(url))
{
try
{
return web.DownloadString(url.GetPrettyURL);
}
catch (Exception ex)
{
// tough luck
//System.Diagnostics.Debug.WriteLine("Error downloading " + url, CRAWLER);
return null;
}
}
else
{
return null;
}
}
